Celestial Sorcerer and Improved Familiar - Help?

[Celestial Pegasus]

I have an unusual thing I'm trying to do; I want to get a Celestial Sorcerer a Familiar. Specifically, a Silvanshee Agathion.

Can anyone suggest some PFS legal routes to do this? Presume a Human, NG alignment, and maximum level of 12. If at all possible, I want to avoid losing any spellcasting progression.

[Conjoy]

Eldritch Heritage Feat going Arcane bloodline.

[Celestial Pegasus]

Thanks for the idea, Conjoy! Actually, your advice lead me to a related feature... apparently a Bloodline Familiar is a thing too. It delays the BONUS Spell acquisition (which I'm totally okay with) and drops Heavenly Fire (which I'm not as okay with, but oh well) to get it right off the bat.

I'll leave this up in case anyone else is interested in the info, but it looks like you pretty well answered my question. I appreciate it!

[samerandomhero]

I am away from my tomes of magical paizo goodness for the moment, but I think there is a archetype of sorcerer called the tattooed sorcerer that gives you a familiar and a lot of ink. This might be another way that lets you keep celestial sorcerer, get a familiar, and maintain full spellcaster progression.
Basically if I recall you give up your first bloodline ability and get a familiar. There are other things too, I don't remember those though.
That would allow you to get the angel kitty with only a feat (improved familiar) and alignment matching the required one.

Conjoys method works too, but it requires eldritch heritage, which itself requires Skill Focus Knowledge, followed by improved familiar.
Which works well too of course.

[Malignor]

As mentioned it will take those 3 feats.

If you've not yet built your character, and you need Skill Focus, you may want to think about this idea...

• Replace bonus feat with Focused Study. Select "skill focus - knowledge" (pick one). This qualifies you for...
  
• Eldritch Heritage (arcane), which requires skill focus (any knowledge), level 3 and CHA 13. This gives you a familiar. Then you just need...
• Improved Familiar and you can get your celestial critter.

Focused Study is an awesome Human trait. Three skill focus feats (rather than one feat of choice) can be very useful. If you already need a Skill Focus feat (like to qualify for eldritch heritage), or if Skill focus gives you an effective edge (like Intimidate for a Dazzling Display fighter... or Perform for a bard... or Perception for almost anyone) then it's a strong choice.
For a Human Sorcerer with Celestial Bloodline, you may consider the three following Skill Focus:

Level 1: Knowledge (pick one, qualify for EldrHeritage-Arcane)
Level 8: Spellcraft, for IDing spells, and your Craft Rods feat at level 9, which allows you to build metamagic rods for feats you don't even have (DC 27). At level 9 with full ranks your bonus becomes 15+INT. At level 10 with full ranks, it's 19+INT, so you can take 10 to "craft metamagic feats" for yourself and your party.
Level 16: Any skill which has 10+ ranks. Or else Perception, because perception is useful for everyone.

EDIT: One more thing while I'm talking about Human Sorcerers. Be sure to look at the option for favored class in Advanced Race guide. +1 spell known per level (whose spell level is LOWER than your highest level spell known) is worthy of drooling over.